Post-Tensioning Cables

 The function of post-tensioning is to place the concrete structure under compression in those regions where load causes tensile stress. Sheathing or ducting houses the prestressing steel. This allows it to move as necessary when the tensioning force is applied after the concrete cures. It reduces and eliminates shrinkage cracking-therefore no joints, or fewer joints, are needed. Cracks that do form are held tightly together. It allows slabs and other structural members to be thinner.  

  Rebar or mesh of steel wires used as a tension device in reinforced concrete and reinforced masonry structures to strengthen and aid the concrete under tension. Concrete is strong under compression but has weak tensile strength. Rebar significantly increases the tensile strength of the structure.  The most common type of rebar is carbon steel, typically consisting of hot-rolled round bars with deformation patterns. Other readily available types include stainless steel and composite bars. The steel reinforcing bars may also be coated in an epoxy resin designed to resist the effects of corrosion mostly in saltwater environments, but also land-based constructions.   Steel and concrete have similar coefficients of thermal expansion, so a concrete structural member reinforced with steel will experience minimal differential stress as the temperature changes.